JP3207892B2 - Magnetostrictive material and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetostrictive material,
The present invention relates to a magnetic material whose length changes when an external magnetic field is applied, and a method of manufacturing the same.

[0002]

2. Description of the Related Art When an external magnetic field is applied to a magnetic body, the magnetic body expands or contracts. This is called magnetostriction. Magnetostriction is applied to, for example, displacement control or drive actuators, magnetostrictive vibrators for generating ultrasonic waves, ultrasonic delay lines, ultrasonic filters, variable frequency resonators, various sensors, and the like.

[0003] Magnetostrictive materials are required to have a high amount of magnetostriction at a low magnetic field strength or a high material strength according to the purpose and application, and are required to have excellent corrosion resistance. As a conventionally known magnetostrictive material having a saturation magnetostriction at room temperature of 300 × 10 ⁻⁶ or more,

(I) Iron and rare earth elements (Tb, Sm, Dy,
Alloys with Ho, Er, Tm) (U.S. Pat.
No. 372, No. 4, 152, 178, No. 3,949,351, No. 4,308, 47
No. 4 specification),

(Ii) alloys of iron group elements and Mn with Tb and Sm (US Pat. No. 4,378,258); (iii) Ti, V, Cr, Mn, Ni, Cu, Nb, M
o, Ta, W, C, Si, Ge, Sn, B, In, L
a, Ce, Pr, Nd, Sm, Gd, Tb, Eu, D
y, Ho, Er, Yb, Lu, Tm, and at least one of Fe,
Material consisting of Al, Co and Ti, V, C
r, Mn, Co, Ni, Cu, Nb, Mo, Ta, W,
C, Si, Ge, Sn, B, In, La, Ce, Pr,
1 of Nd, Sm, Gd, Eu, Er, Yb, Lu, Tm
And a magnetostrictive material comprising Tb, Dy, Ho, and Fe (JP-A-53-64798). These magnetostrictive materials are an intermetallic compound of Fe and a rare earth element R called an RFe ₂ Laves type intermetallic compound, or a material to which other elements such as a transition metal are added. It has a saturation magnetostriction value λs that is one to two orders of magnitude greater than the magnetostrictive material used and is called a giant magnetostrictive material.

Among the RFe ₂ Laves type intermetallic compounds, T
bFe ₂ has a large magnetostriction when the external magnetic field strength is high, for example, at an external magnetic field strength of about 20 to 25 kOe, but does not have a sufficient magnetostriction when the magnetic field strength is low. Therefore, Tb
(Tb, Dy) Fe ₂ , in which a part of is replaced by Dy, is widely used as a magnetostrictive material having an improved magnetostriction at low magnetic field strength. SmFe ₂ is used as a negative magnetostrictive material.

When an apparatus using such a magnetostrictive material is used outdoors, it is necessary to assume a considerably wide operating temperature range. For example, devices using magnetostriction are applied to various valves for automobiles and the like. In this case, it is necessary to guarantee a substantially linear operation from a high temperature of about 150 ° C. to a low temperature of about 50 ° C. below zero. However, (Tb, Dy) Fe
No. ₂ has poor temperature characteristics, and the optimum composition ratio of Tb and Dy at room temperature causes a change in magnetic anisotropy particularly at a low temperature of 0 ° C. or lower, so that the magnetostriction is greatly reduced. Therefore,
In order to use the device in a harsh environment, it is required to improve the temperature characteristics of the magnetostrictive material. Further, when used in a refrigeration facility or the like, a large amount of magnetostriction is required, for example, at −40 ° C. or lower.

[0008] Among the RFe ₂ Laves-type intermetallic compounds, those having an extremely large theoretical value of λs are CeF
e ₂ and PrFe ₂ (sensor technology 1990 2
Monthly, p. 36), is expected to outperform conventional giant magnetostrictive materials. Pr and Ce are expressed as T
Resources are abundant and cheaper than b.

However, 32000 is required for the synthesis of PrFe _2.
An ultra-high pressure of about 35,000 atm and a high temperature heat treatment of about 1000 ° C are required. CeFe ₂ is promising as a material having a large amount of magnetostriction at a low temperature, but its use is limited because it requires a long time for its synthesis and its Curie temperature is lower than room temperature.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetostrictive material which exhibits a larger magnetostriction at low temperatures than conventional giant magnetostrictive materials and is easy to manufacture. Aim.

[0011]

This and other objects are achieved by the present invention which is defined below as (1) to (3). (1) A magnetostrictive material having an atomic ratio composition represented by the following formula. Formula (RM _x Ce _1-x ) T _y (where RM is Pr or Nd, T is at least one of Fe, Co and Ni, and 0.1 ≦ x ≦ 0.9, 1 0.0 ≦ y ≦ 2.0) (2) The method for producing a magnetostrictive material according to the above (1), wherein the molten base material alloy is brought into contact with a cooling base and quenched.
A method for producing a magnetostrictive material, comprising a step of subjecting the obtained quenched alloy to hot working. (3) The method for producing a magnetostrictive material according to (2) above, wherein the quenched alloy is pulverized and then subjected to hot working.

[0012]

Magnetostrictive material of the present invention having the composition represented by [action] The above formula shows the magnetostriction surpass (Tb, Dy) conventional super magnetostrictive material _2, such as Fe. In particular, a large magnetostriction (Δl / l) of 300 ppm or more can be realized even in a low temperature range of −10 ° C. or less.

[0013] The magnetostrictive material of the present invention does not require ultra-high pressure and high-temperature heat treatment at the time of production, and is easy to produce.

[0014]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

The magnetostrictive material of the present invention has an atomic ratio composition represented by the following formula. In the formula _{(RM x Ce 1-x)} T y above formula, RM is Pr or Nd, T is F
e, at least one of Co and Ni, 0.1 ≦ x ≦ 0.9, preferably 0.3 ≦ x ≦ 0.7, 1.0 ≦ y ≦ 2.0, preferably 1.5 ≦ y ≦ 2.0.

If x is too small, the Curie temperature is so low that it has no magnetism at room temperature, and it is very easily oxidized, which may cause ignition, making handling difficult. Further, when x = 0, it takes a long time for the composition. If x is too large, the ratio of a different phase other than (RM, Ce) Fe ₂ will increase unless the pressure during hot working described later is made extremely high, and the magnetostriction will decrease.
This is most noticeable when x = 1. And 0.3
If ≦ x ≦ 0.7, a large amount of magnetostriction can be obtained at room temperature and low temperature even when the pressure during hot working is reduced,
In particular, when Pr is used as RM and 0.4 ≦ x ≦ 0.6, an extremely large amount of magnetostriction is realized at a low temperature.

When y <1.0, the rare earth element rich phase increases, and the magnetostriction decreases. If y> 2.0, an Fe-rich phase precipitates and the magnetostriction decreases.

In the above formula, when y is less than the above range, the rare earth element rich phase increases, and when it exceeds the above range, a hetero phase such as (RM, Ce) Fe ₇ phase occurs, and in each case, the magnetostriction decreases.

Since T has a Curie point of room temperature or higher, it is preferable to use Fe alone or one obtained by substituting a part of Fe with Co. Further, it is conceivable that the strength may be improved by forming a rare earth element and an alloy thereof by substituting Mn, Cr, Mo, or the like, and therefore, these elements may be contained.

Although there is no particular limitation on the method for producing the magnetostrictive material of the present invention, it is preferable to use a method of hot working after rapid quenching.

In this method, first, a molten metal alloy is brought into contact with a cooling substrate such as a cooling roll and quenched to produce a rapidly quenched alloy such as a ribbon, a flake (flake), or a grain.
The quenching condition is not particularly limited, and may be appropriately determined according to the alloy composition and the like. Although the microstructure of the quenched alloy varies depending on the cooling rate, it is usually in an amorphous state or a state in which fine crystals such as a rare earth element simple substance and a (RM, Ce) Fe ₇ phase are mixed.

Next, after pulverizing if necessary, hot working is performed. The conditions for hot working are not particularly limited, but the applied pressure is 100 kgf / cm ² or more, particularly 1000 kgf / cm ²
It is preferable to make the above. In the present invention, the applied pressure during hot working is 20,000 kgf / cm ² or less,
A large magnetostriction amount can be obtained even when the amount is not more than 00 kgf / cm ² . Further, the holding temperature is preferably 400 to 700 ° C,
More preferably, it is 500 to 600 ° C. In this case, the temperature of the workpiece is preferably about 500 to 850C, more preferably about 600 to 750C.

After hot working, it is cooled to room temperature.

For the hot working, an ordinary hot press may be used. However, if plasma activated sintering (PAS), which can be densified in a short time and can be heated at a high speed, can be used,
Oxidation can be prevented, and the cost is also advantageous. In plasma-activated sintering, quenched alloy particles are activated in plasma and then sintered. In this case, the plasma generation method, the plasma activated sintering apparatus to be used, and the like are not particularly limited, but a preferred example will be described using the plasma activated sintering apparatus 1 shown in FIG.

First, quenched alloy particles 5 are put between the punches 3 in the mold 4 of the apparatus 1. Next, pressing is performed with the punches 3 and 3 and a current is caused to flow between the electrodes 2 and 2 in a vacuum to generate plasma. The plasma generation current usually has a pulse width of 20 × 10
A pulse current of about ^{−3 to} 900 × 10 ⁻³ seconds is used.

The more detailed mechanism is as follows.

When the pulse voltage applied between the electrodes 2 and 2 reaches a predetermined value, the contact surface between the electrode and the quenched alloy particles and the contact surface between the quenched alloy particles cause dielectric breakdown and discharge occurs. At this time, the surface of the quenched alloy particles is sufficiently purified by the electrons that have jumped out of the cathode and the ion bombardment generated at the anode. Also, the discharge impact pressure due to the spark is applied to the particles. Then, the discharge impact pressure gives a strain to the particles and improves the diffusion speed of atoms.

The Joule heat generated by the subsequent energizing current spreads around the contact point, and makes the rapidly cooled alloy particles plastically deformable. In particular, since the atoms at the contact portion are activated and easily moved, the gap between the particles is reduced by simply applying pressure to the quenched alloy particles, and the atoms start to diffuse. In addition, since an electric field is present, metal ions easily move electrically.

As a result, the sintering time can be shortened, and oxidation of the particles can be prevented.

The conditions for such plasma-activated sintering are generally preferably as follows. Press pressure: about 1000 kgf / cm ² or more Plasma generation time: about 1 to 3 minutes Plasma atmosphere: 10 ⁻³ to 10 ⁻⁵ Torr Maximum temperature during sintering: about 500 to 600 ° C. (The temperature of the sintered body is 600 to (Approx. 750 ° C) Holding time at maximum temperature: 0 to 10 minutes Conducting current: 1500 to 3000A

The above description is merely an example. In addition, the atmosphere may be an inert gas such as Ar, an N ₂ gas having a controlled oxygen partial pressure, or the like. It is appropriately selected depending on the method and the like.

By the above-mentioned hot working, usually,
Although a polycrystalline magnetostrictive material composed of (RM, Ce) Fe ₂ phase crystal grains and rare earth element-rich crystal grain boundaries is obtained, the magnetostrictive material of the present invention may be a single crystal.

It is to be noted that other general alloy production methods such as arc melt method, Bridgman method, directional solidification method, zone melt method, high frequency melting method, powder metallurgy method, centrifugal casting method, etc. The method may be selected to produce the magnetostrictive material of the present invention. These production methods are described, for example, in US Pat. Nos. 4,308,474 and 3,949,35.
No. 1, No. 4,378,258, No. 4,375,372, No. 4,158,368
No. 4,152,178, No. 4,
609,402, 4,374,665, JP-B-61-33892, and JP-A-58-3.
294, etc. The magnetostrictive material manufactured by these methods is preferably subjected to an annealing treatment as needed.

The magnetostrictive material of the present invention may be anisotropic if necessary.

[0035]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention.

The molten alloy material was rapidly quenched by a single roll method to obtain a flaky quenched alloy. Then, FIG.
The quenched alloy was sintered using a plasma-activated sintering apparatus having the structure shown in Table 1 to produce a magnetostrictive material sample shown in Table 1 below. The plasma generation method and sintering conditions were as follows. Plasma generation method: pulse current with pulse width of 30 × 10 ⁻³ seconds Press pressure: 2000 kgf / cm ² Plasma generation time: 1 minute Plasma atmosphere: 5 × 10 ⁻⁵ Torr Maximum temperature during sintering: mold temperature 550 ° C. ( Sintered body temperature is 6
70 ° C.) Holding time at the highest temperature: 1 minute Current: 2300 A Sintering atmosphere: 5 × 10 ⁻⁵ Torr

Table 1 shows the atomic ratio composition of each sample. For these samples, the amount of magnetostriction was measured by changing the environmental temperature at the time of measurement. The measurement of the magnetostriction was performed with a strain gauge. The applied magnetic field strength during the measurement was 1 kOe. Table 1 shows the results.

FIG. 2A shows an X-ray diffraction chart of Sample No. 3, and FIG. 2B shows an X-ray diffraction chart of Sample No. 6. RFe ₂ peaks are observed in these charts.

For comparison, (Tb, Dy) Fe ₂ sample No. 1 was prepared in the same manner as described above.
The same measurement as above was performed for this comparative sample. Table 1 shows the results.

[0040]

[Table 1]

The effects of the present invention are apparent from the results of the above examples. That is, in the sample Nos. 2 to 4 and 6 of the present invention, the amount of magnetostriction was not reduced down to −50 ° C., indicating that the sample can be used in an extremely wide temperature range. On the other hand, in the comparative sample No. 1, the amount of magnetostriction at a low temperature was remarkably reduced, and a stable amount of magnetostriction was not obtained. In addition, sample No. 5 showed RF as a result of X-ray diffraction.
It was found that no e ₂ phase was formed.

[0042]

According to the magnetostrictive material of the present invention, in the RFe ₂ Laves type intermetallic compound, Pr and Ce or N
d and Ce are combined. Thereby, (Tb, D
y) An amount of magnetostriction exceeding that of a conventional giant magnetostrictive material such as Fe ₂ can be obtained at a low temperature and can be used in a wide temperature range. In addition, the magnetostrictive material of the present invention does not require ultra-high pressure and high-temperature heat treatment at the time of production, and is easy to produce.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a plasma activated sintering apparatus used for producing a magnetostrictive material of the present invention.

FIGS. 2 (a) and (b) show X of the magnetostrictive material of the present invention.
It is a line diffraction chart.

[Description of Signs] 1 Plasma activated sintering device 2 Electrode 3 Punch 4 Formwork 5 Quenched alloy particles

Continuation of front page (56) References JP-A-1-246342 (JP, A) JP-A-3-183738 (JP, A) JP-A-1-290733 (JP, A) JP-A-4-362159 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 303 C22C 19/00 H01L 41/20

Claims (3)

(57) [Claims] 1. A magnetostrictive material having an atomic ratio composition represented by the following formula: Formula (RM _x Ce _1-x ) T _y (where RM is Pr or Nd, T is at least one of Fe, Co and Ni, and 0.1 ≦ x ≦ 0.9, 1 0.0 ≦ y ≦ 2.0.) 2. The method for producing a magnetostrictive material according to claim 1, further comprising a step of bringing a molten metal alloy into contact with a cooling base to quench the alloy, and subjecting the obtained quenched alloy to hot working. A method for producing a magnetostrictive material. 3. The method for producing a magnetostrictive material according to claim 2, wherein hot working is performed after the quenched alloy is pulverized.